The present invention relates to magnetic hard drive manufacturing. More specifically, the present invention relates to a system for treating (e.g. polishing to remove defects) the surface of a media, such as a magnetic hard disk, while in operation, such as during electrical testing.
In a continuing effort to improve magnetic hard drive performance, efficiency, and reliability, different methods are utilized to improve quality control. One method in the art includes cleaning and burnishing a hard disk following the deposition of thin film layers to remove debris and asperities from the surface. To support ever-increasing areal-density requirements, parameters such as flying height, disc roughness, and carbon thickness are continually reduced. The successful manufacture of disks capable of meeting these parameters requires improvements to hard disk preparation.
In the art, a burnishing head, which replaces the slider of a hard drive suspension such as a head gimbal assembly (HGA), is used to swab the disk surface on-line during dynamic electrical testing (DET) of magnetic heads. Such burnishing heads are typically created by diamond-grinding means, which provides a burnishing surface that can result in a dispersal of unwanted head particles as well as a propensity to chip. Further, the typical burnishing head design can cause abrupt takeoffs as well as high dynamic pitch angles, being unable to provide a burnishing surface substantially parallel to the media surface (hard disk) as is needed for optimal polishing.
Several different burnishing head designs are currently utilized in media manufacture (e.g. U.S. Pat. No. 6,267,645; U.S. Pat. No. 6,249,945; and U.S. Pat. No. 5,782,680). Some heads have a burnishing ridge providing a burnishing edge that extends across the entire widthwise surface of the head. Other head designs have burnishing pads only on various points of the burnishing surface, but have a lengthwise channel between two members.
An ineffective burnishing head may result in a lower glide yield, while an overly aggressive glide head may result in scratches and damage to the disk surface, which can lead to disk corrosion. The most commonly used burnishing head has a polyangular design, such as rectangular and triangular, with a grinding wheel-cut waffle pattern.
FIG. 1 provides a burnishing head as is typical in the art. The fabrication of such ‘waffle’ burnish heads is accomplished by slotting the head substrate with a diamond grinding wheel (See FIG. 2) and taper-lapping. Unfortunately, utilizing these manufacturing methods (to achieve this design) results in a high likelihood of micro-fractures in the ceramic and a high level of particulate production. The sharp corners 102 (typical) of this design are stress concentration areas that are easily broken off and embedded into the disc. Further, as stated, the burnishing head typically has a taper 104 at the leading 106 and/or trailing 108 edge.
FIG. 2 provides an illustration of the grinding steps for creating the ‘waffle head’ pattern as is used in the art. First, several parallel grooves are carved out of the burnishing material with a grinding wheel in a diagonal direction 202. Second, several parallel grooves are carved out with the grinding wheel in the other (perpendicular) diagonal direction 204. Third, the material is cut entirely through in a direction perpendicular to the material's length 206, yielding individual (‘waffle head’) burnishing pads 208.
Such heads are designed for media manufacture to burnish rough surfaces and are too aggressive to adapt to swab the testing surface of media during DET of magnetic heads. It is therefore desirable to have a system for treating (e.g. polishing to remove defects) the surface of a media such as a magnetic hard disk while on-line without the aforementioned problems.